This invention relates generally to the field of pumps, in particular pumps for automotive vehicles, that are designed to pump liquid fuel from a tank through a fuel system to an engine.
In a vehicle powered by an internal combustion engine, a motor operated fuel pump may pump liquid fuel from a tank through a fuel system to the engine. Typically, fuel pumps such as those in the prior art utilize a rotating impeller driven by a motor to move fluid from an inlet port to an outlet port.
In part due to particulate contaminants that are present in liquid fuel such as conventional-grade gasoline, the parts of the fuel pumps may become worn as the particulates contact surfaces of moving parts or componentry near these parts at high speed. This decreases the efficiency of the pump and, in some cases, can lead to pump failure. Especially effected are the plastic impellers used by these fuel pumps. The pumping chamber walls may also become worn, creating a greater space than is necessary between the impeller and the walls of the pump and thereby further reducing efficiency.
U.S. Pat. No. 5,921,746 attempted to solve this problem using a new guiding technique wherein particulate and other contaminants are routed into a separate contaminate channel, thereby keeping them away from the impeller. However, the special channel is difficult to manufacture, as it must be machined to have a varying depth such that the depth of the channel decreases as the contaminants travel to the end of the channel. The dimensional requirements of this channel are also not conducive to mass production, thereby resulting in increased costs for manufacturing the pump.
The present invention provides, in one embodiment, a fuel pump for pumping fuel from an inlet port to an outlet port. A housing made up of a body piece and a cover piece encloses an impeller. The impeller has a vaned periphery and an outer ring connected by spokes. An inlet hole is defined within the cover piece for fuel to enter the pump. An outlet hole is defined within the body piece for fuel to exit the pump into an internal chamber. A first main semicircular shaped channel is defined circumferentially into the cover piece and extends in an annular fashion around the cover piece. The body piece has a second main semicircular channel as well as at least one annular groove. In the preferred embodiment of the invention, there are two annular grooves, one connected directly to the second semicircular channel, and one around the peripheral edge of the body piece at the point where it contacts the cover piece.
In a further embodiment of the invention, the main channel in the cover begins at the inlet hole and the main channel in the body ends at the outlet hole, allowing the fuel to enter and leave the chamber. The end of the main channel in the cover expands outwardly at the end, and inclines upwardly, ramping towards the impeller. The end of the main channel in the cover aligns with the end of the main channel in the body opposite the outlet hole. An annular groove is in fluid communication with the main channel in the body via the outlet hole and at the portion of the channel in the body that aligns with the expanded potion of the channel in the cover. In the preferred embodiment of the invention, the other annular groove is in fluid communication with the main channel in the cover when the pieces are assembled.
In the present invention the annular grooves preferably are of a constant depth. This allows for simplified, economical manufacturing. There is also a space between the impeller and the outer wall of the body piece such that the space contacts the annular grooves when the pump is assembled.
Another embodiment of this invention has the same general features as the embodiment above, but the second annular groove is machined into the cover piece instead of the outer edge of the body piece. This annular groove contacts the expanded portion of the first main semicircular channel and at another point at the inlet hole.
In yet another embodiment of the invention, generally the same features are provided as in the embodiments above, but the housing is one solid piece, rather than a body and a cover piece. The first annular groove and first main semicircular channel are machined into the housing below the impeller. The second annular groove and second main semicircular channel are machined into the housing above the impeller.
The invention may also be embodied in a method for substantially preventing contaminants in liquid fuel from coming into contact with a substantial portion of a vaned impeller. The method includes the steps of routing the contaminants into annular grooves that are connected to the main semicircular channels in the body and the cover pieces. The contaminants are retained within the annular grooves and away from the impeller vanes before being expelled with the rest of the liquid fuel through an outlet.
In the present invention, the annular grooves allow for the contaminants to substantially avoid the impeller, thus reducing wear on the pump parts and maintaining a higher efficiency. Furthermore, since the annular grooves are kept at a constant depth, they are efficient to machine. This allows for effective mass production of the fuel pump.
It is to be understood that both the preceding summary and the following detailed description are intended to be exemplary and explanatory and are intended to provide a further explanation of the invention claimed. The invention will be best understood by reference to the following detailed description read in conjunction with the accompanying drawings.